The cooling liquid used in the cooling systems for liquid cooled engines typically includes an ethylene glycol based antifreeze to effect efficient heat transfer and prevent freezing of the cooling liquid. While ethylene glycol based antifreeze is effective for these purposes, the ethylene glycol in the cooling liquid can be very corrosive to the cooling system. Also, a small percentage of the ethylene glycol will break down during repeated heating and cooling of the cooling liquid to form glycolic or formic acids which can attack the various metals exposed in the cooling system. Additionally, cooling systems often contain particles which were left in the system when the system was assembled, (e.g., rust or particles remaining from the casting process) or which were subsequently added to the system or produced in the system by chemical reactions described above, which particles circulate with the liquid as it is pumped through the cooling system. These particles can plug or coat portion of the passageways in the cooling system (such as in the heater core) and decrease the efficiency of the cooling system.
Filter-conditioner assemblies have been provided for some engines (see U.S. Pat. No. 3,645,402) to both filter the cooling liquid and add chemicals to the cooling liquid to restrict such chemical reactions. Heretofore, however, such known filter-conditioners have been designed for use in pressurized portions of cooling systems which necessitates a housing for the filter-conditioner that can withstand pressures of over 12 psi above atmospheric pressure, and thus have been very expensive for use to retrofit conventional automobiles which have typically not been provided such filter-conditioners at the factory. Thus to protect their cooling systems, automobile owners have typically resorted to either changing the ethylene glycol based antifreeze in the cooling systems of their automobiles more frequently than they might otherwise desire, and/or to adding chemicals to treat the cooling liquid directly to the cooling system.